The present invention relates generally to seals of the type employed to prevent leakage between mechanical members. More particularly, the present invention relates to an improved seal wherein trimming indicia are used as visual targets for setting up equipment to trim a waste portion from a molded seal body during manufacture.
To work properly, a manufactured seal, particularly a lip seal such as a wheel seal for an automobile, must be produced according to strict specifications. A wheel seal is used to keep the bearings of the wheel lubricated while protecting the bearings from outside contaminants which could interfere with bearing operation. Prior art seals have been molded into a final shape without any trimming. Such seals are designed toward a mean optimal acceptable value and have the advantage of normally consistent production. Yet, untrimmed molded seals often cannot meet required design specifications.
Trimmed seals are also produced according to strict design specifications, having the added advantage of higher initial sealing reliability than non-trimmed molded seals. Unfortunately, it has been very expensive and time-consuming to trim seals in commercial settings. Typically, an operator sets up a trimming operation and then trims a sample seal. A destructive method involving sectioning is then used to inspect samples of the final seals. An iterative process, which is both time-consuming and subject to errors, takes place until a sample seal appears to be correctly trimmed.
Even if a sample seal has been properly inspected, variables associated with a trimming operation may result in unacceptable seals being produced, particularly over time as the trimming operation continues. If this happens, there is generally no non-destructive way to distinguish properly trimmed seals from unacceptable seals.
It is known to have surfaces on seals to provide some guidance for the trimming operation. Typically, such surfaces have been used to guide the entrance of a cutting element into the seal. While such guidance is somewhat beneficial, it still possible for the initially guided cutting element to exit the seal body at a position which results in an unacceptable final trimmed seal part.